answer:Here’s an informative take on password complexity from the web comic xkcd.com. Wikipedia has an article on the RSA algorithm for public-key cryptography, based on the fact that it’s easy for a computer to multiply two large prime numbers together, yet nearly impossible to do the inverse operation, which is to decompose a product into composite prime numbers. This was invented in the late 1970s, so not really a “hot topic” anymore. Two recent books on related topics that I found interesting (and easy to read) are The Code Book by Simon Singh (2000) and The Information by James Gleick (2011). Hope that helps.